Q23 of 47 Page 1

Answer the following with reason :

(a) Is (NH–CHR–CO)n , a homopolymer or copolymer ?


(b) Is PVC a condensation or addition polymer ?


(c) Is Bakelite a thermoplastic or a thermosetting plastic ?


(a) Homopolymer means that the polymer is formed of repeating units of the same monomer whereas copolymer means polymer formed from more than one monomer.


As (NH–CHR–CO)n consists of ‘n’ number of repeating units of the same monomer ‘NH–CHR–CO’, it is a homopolymer.


(b) PVC is formed from vinyl chloride monomer through free radical mechanism. Vinyl polymerisation proceeds in three steps:


(1) Chain initiation- The radical initiator is broken into the intermediate free radicals by various means(eg. Sunlight or heat).


(2) Chain propagation – The free radicals combine with monomers to form bigger intermediate species.


(3) Chain terminating – The radical intermediates join with one another with the help of chemical bonds.



It is addition polymer as it is formed by the addition of the same monomeric unit of vinyl chloride.


(c) Bakelite is a thermoplastic. As a result they are poor conductors of electricity and subsequently they are highly heat resistant. So they are used in switches to prevent us from getting electrical shocks.


More from this chapter

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21

Give one chemical test to distinguish between the following :

(a) Phenol and 1-propanol


(b) Ethanol and dimethyl ether


(c) 1-propanol and 2-Methyl-2-propanol


OR


Write the products of the following reactions :


(i) CH3-CH2-O-CH3 + HI


(ii)


(iii)


 22

Account for the following, supporting your answer with diagrams orequations wherever possible :

(a) Diazomium salts of aromatic amines are more stable than those of aliphatic amines.


(b) Methylamine in water reacts with ferric chloride to precipitate


hydrated ferric oxide.


OR


Arrange the following in decreasing order of pKb giving reason :


(a) Aniline, p-nitroaniline and p-toluidine


(b) C2H5NH2, (C2H5)2NH, (C2H5)3N in gaseous state


 24

Answer the following :

(a) What is tincture of iodine ? What is its use ?


(b) What are the main constituents of dettol ?


(c) Label the hydrophilic and hydrophobic parts of the given


compound :


CH3(CH2)16COO(CH2CH2O)nCH2CH2OH


 25

(a) Draw the graph between vapour pressure and temperature andexplain the elevation in boiling point of a solvent in solution.

(b) Determine the osmotic pressure of a solution prepared by


dissolving 25 mg of K2SO4 in 2 litres of water at 25°C assuming it to be completely dissociated. (Atomic masses K = 39 u, S = 32 u, O = 16 u)


OR


(a) Write two characteristics of non-ideal solution.


(b) 2 g of benzoic (C6H5COOH) dissolved in 25 g of benzene shows a depression in freezing point equal to 1.62 K. Molal depression constant for benzene is 4.9 K kg mol–1. What is the percentage association of acid if it forms dimer in solution ?